The objective of the proposed research is to determine the influence of meal pattern and diet composition on the control of energy balance in appropriate animal models. Rats, genetically obese (ob/ob) mice, pigs and dogs will be utilized. Specifically, the proposed investigations will consider the influence of meal pattern and the relationship between meal pattern and physical activity on energy retention in the pig. The effect of diet composition, thyrotropin releasing hormone and thyroxine on the development of obese mice during the immediate post-weaning period will be ascertained. The influence of gluttony on energy efficiency will be evaluated in dogs. The biochemical mechanism(s) involved in dietary-induced alterations in energetic efficiency will be investigated. Because (Na plus K) ATPase has recently been associated with the thermogenic response observed in cold exposure, thyroxine or ethanol treatments, initial studies will focus on the possible involvement of (Na plus K) ATPase in dietary-induced thermogenesis. The results of the proposed investigations should increase our knowledge of the interaction between diet and energy metabolism and should contribute to our understanding of the control of obesity and disease states associated with obesity.